Ramallah, West Bank -- An autopsy showed that an Arab teenager who Palestinians say was killed in a revenge attack was burned to death, officials said Saturday, while Palestinian militants fired two rockets toward a major southern city deeper into Israel than any other attack in the current round of violence.

The Israeli military said its "Iron Dome" defense system intercepted the rockets that were aimed at Beersheba. The military also said at least 29 other rockets and mortars were fired from the Gaza Strip at Israel over the weekend. It said it had retaliated with air strikes on militant sites in Gaza.

Clashes between Israeli police and Palestinian protesters spread early Saturday from Jerusalem to Arab towns in northern Israel as hundreds of people took to the streets and threw rocks and firebombs at officers who responded with tear gas and stun grenades, police said.

Palestinian Attorney General Abdelghani al-Owaiwi said he received initial autopsy results from a Palestinian doctor who was present at the autopsy in Tel Aviv. He said it shows that 16-year-old Palestinian Mohammed Abu Khdeir, whose death has sparked large protests, suffered burns on "90 percent of his body."

"The results show he was breathing while on fire and died from burns and their consequences," al-Owaiwi said.

His account provided the first details of the preliminary findings to be made public. The Israeli Health Ministry could not be reached for comment.

The autopsy found evidence that Abu Khdeir had breathed in the flames as burns were found inside his body, in his lungs, bronchial tubes and his throat, al-Owaiwi said. He also said the young man had suffered wounds on the right side of his head apparently from impact with a rock or another hard object.

Abu Khdeir's charred body was found in a forest Wednesday after he was seized near his home. Palestinians immediately accused Israeli extremists of killing him to avenge the deaths of three Israeli teens who had been abducted and killed in the West Bank. Israeli police said an investigation is still under way and they have not yet determined who killed the boy or why.

Israeli leaders have widely condemned the killing of the Palestinian youth.

Palestinians took to the streets in protests after news of the boy's death on Wednesday and clashed with police in East Jerusalem. Riots erupted in East Jerusalem on Friday as thousands of Palestinians massed for the boy's burial.